GUMS & STABILIZERS

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What is Hydrocolloid?

• Food hydrocolloids is a range of polysaccharides and proteins, also known as 'water soluble gum', 'gum', 'stabilisers'.
• Primary functions: Thickening agents, Gelling or texturizing agents.
• Secondary functions: Stabilisation of emulsions, suspension of particulates, control of crystallisation, encapsulation, formation of film.

Factors affect gum properties

• molecular weight
• monosaccharide composition
• type of chains
• number of side chains
• distribution of side chains

Main classes of hydrocolloids

• derivatives from exudation or sap of trees (e.g. cellulose, gum arabic, gum karaya, gum ghatti, gum tragacanth)
• extract from seed (e.g. guar gum, LBG, tara gum, tamarind gum)
• extract from seaweeds (e.g. agar, carrageenan)
• microbial gums (e.g. xanthan, dextrun,curdlan)
• extract from tubers (e.g. konjac)
• extract from plant parts (e.g. starch, pectin, cellulose)

Main Hydrocolloids - Thickeners

1. xanthan gum
2. carboxymethylcellulose
3. methylcellulose and hydroxypropyl cellulose
4. galactomannas (guar and LBG)

Main hydrocolloids - Gelling agent

- Thermoreversible gelling agents

1. gelatin
2. agar
3. kappa carrageenan
4. iota carrageena
5. low methoxy (LM) pectin
6. gellan gum
7. methyl cellulose and hydroxypropyl cellulose
8. xanthan gum and locust bean gum or konjac mannan

- Thermally irreversible gelling agents

1. alginate
2. high methoxyl (HM) pectin
3. konjac mannan
4. locust bean gum

Pectin

• derived from peel of citrus fruits, apple pomace, sugar beet, sunflower heads.

• types of pectin---High methoxyl pectin (HMP), DE> 50% and Low methoxyl pectin (LMP), DE< 50%

High methoxyl pectin (HMP)

• DE---58% to 75%
• to form gel, soluble solid content 55-85%, pH 2.8-3.8. (e.g. jam and jellies)
• ultrarapid/rapid set (DE as high as 77)---used in jam with whole fruits, to ensure uniform distribution of fruits particles.
• slow set (DE~58) ---used in very acid fruits such as blackcurrant to avoid premature gelation.

Low methoxyl pectin (LMP)

• two sub-groups---Conventional low methoxyl pectin (LMP) and Amidated low methoxyl pectin (ALMP).
• form gels in presence of calcium ions, low soluble solid content, wide pH range (1-7). Soluble solid can up to 85%.
• LMP - less calcium ion reactive than ALMP---used as thickening agent in yogurt fruits.
• ALMP - very calcium ion reactive---used in low sugar fruits preparatuin (e.g. low-sugar jam and jellies).

Guar Gum

• more highly substituted than LBG, more soluble, hydrates fully in cold water giving high viscosity
• non-gelling---used as viscosity builder, stabilizer, water binder
• very stable from pH 4-10

Xanthan Gum

• completely soluble in cold water, produce high viscosity at low concentration
• excellent stability to heat and pH
• viscosity remain unchanged across temperature range (0-100 degree celcius), pH 1-13
• used as a thickening, suspending and stabilizing agents.

Cellulose Derivatives

• alkaline treatment converts cellulose into ether
• examples---carboxymethylcellulose (CMC), hydroxypropyl methylcellulose (HPMC)
• very clear solution, stable over pH 4-10
• used as thickener, suspending and stabilizing agents. Modify flow characteristics.
• use in fried foods---create a barrier to oil absorption, retard loss in moisture, improve adhesion of batter.

Carrageenan

• three types of carrageenan: kappa, lamda and iota
• in a concentration as low as 0.5%, kappa and iota carrageenan can form thermoreversible gel upon cooling of hot aqueous solution containing various cations.
• some examples of food application for carrageenan: water dessert gels, chocolate milk, canned and processed meat, ice-cream, cold prepared custard.

Alginate

• made up of blocks of D-mannuronic acid (M-blocks) and L-glucuronic acid (G-blocks)
• can form gel in presence of calcium ion in cold water; the gels is thermo-irreversible
• provide excellent stabilizing effects in frozen products. (e.g. ice-cream)
• act as thickeners and stabilizers in beverages (e.g. dry mix fruit drinks)
• propylene glycol alginate with emulsification property, used as stabilizer in emulsion (e.g. mayonnaise)

Gum Arabic

• dissolve easily in hot/cold water
• least viscous and most soluble of all hydrocollods-up to 55%solid concentration can be used
• encapsulate volatile flavour
• promote stabilisation in beer foam
• give viscosity and emulsifying properties. Used as emulsifier and stabilizer in soft drinks

Locust Bean Gum (LBG)

• insoluble in cold water, must be heated to dissolve-max viscosity develop when heated to~95 degree celcius, then cooled
• does not form gel by itself but form gel when combined with xanthan gum
• non-ionic, stable over pH 3.5-11.0
• primary functions: hickening, stabilization of emulsions, inhibition of syneresis
• used in canned foods, sauces, desserts, ice-cream, processed meat

Relative Ranking of Gum Properties

1. solution claity
2. solubility at various temperature
3. gelling vs thickening
4. suspension ability
5. natural vs not natural
6. ability to tabilize protein at low pH
7. acid stability
8. relative cost per unit weight

What is Gelatin?

• edible natural foodstuff
• raw material used---skin (pigskin and hide split) and bone taken from slaughtered animals
• collagen contained in raw materials is starting material for manufacture of gelatin
• type A---derived from acid processed materials (porkskin)
• type B---derived from alkaline or lime processed materials (calf hides,ossein)
• forms thermally eversible gel wit water
• melting temperature <35 degree celcius---give the melt-in-mouth properties, rapid release of aroma
• used in gelled jelly, yogurt, fruit iuices, top quality ice-cream and frozen produts, gummy bears, etc.

Typical functional properties

• gel formation
• water binding
• texturizing
• thickening
• emulsion formation anfd stabilisation
• foam formation and stabilisation
• film formation
• adhesion/cohesion
• protective colloidal function